Bariatric Surgery In Hypertrophic Cardiomyopathy Patients
Overview
Existing research has hinted at a link between obesity and increased risk of acute cardiovascular events. Bariatric surgery has been shown to mitigate this risk; however, its impact on patients with both obesity and hypertrophic cardiomyopathy (HCM) remains unclear. This study aimed to assess whether bariatric surgery reduces the risk of cardiovascular-related acute care events in individuals with HCM.
In this population-based investigation, the bariatric surgery group comprised HCM patients who underwent the procedure between January 2004 and December 2014. The control group included individuals with obesity and HCM who underwent non-bariatric elective intra-abdominal surgery during the same period. The primary outcome was cardiovascular-related acute care utilization (emergency department visits or unplanned hospitalizations for cardiovascular disease) within the first year post-surgery. Data from the SPARCS database, a comprehensive ED and inpatient database in New York State, were employed.
Logistic regression models, accounting for relevant variables such as age, sex, prior ED visits, hospitalizations for cardiovascular disease, and Elixhauser co-morbidity measures, were utilized. Propensity score matching and inverse probability treatment weighting analyses were also conducted. The study involved 207 adults with obesity and HCM, with 147 undergoing bariatric surgery and 60 in the control group. No significant difference in risk was observed during the initial 1–6 months post-surgery. Conversely, in the 7–12 months post-surgery period, the bariatric surgery group exhibited a significantly lower risk of cardiovascular-related acute care events (adjusted odds ratio 0.23; 95% CI 0.068–0.71; P= 0.01) compared to the control group. Propensity score-matched and inverse probability treatment weighting analyses validated these findings.
Introduction
Hypertrophic cardiomyopathy (HCM) stands as the most prevalent genetic heart disease in the United States, with its clinical manifestation influenced by a complex interplay of genetic and environmental factors. Obesity, a significant modifiable risk factor for various cardiovascular conditions, including dyslipidemia, type 2 diabetes mellitus, hypertension, and heart failure, also impacts HCM. Studies have demonstrated a correlation between body mass index (BMI) and the extent of hypertrophy in HCM, along with an association between obesity and HCM-related complications such as ventricular arrhythmia, heart failure, atrial fibrillation, and stroke.
Current guidelines advocate weight loss in individuals with both obesity and HCM to mitigate the risk of unfavorable cardiovascular events. Bariatric surgery, acknowledged as the most effective means to achieve substantial and sustained weight loss, presents a potential intervention. Previous research in non-HCM populations has linked significant weight loss to a reduced risk of acute cardiovascular events like myocardial infarction, stroke, heart failure exacerbation, angina, and hypertensive crisis.
Despite this, evidence regarding the relationship between weight loss and the risk of acute cardiovascular events in individuals with obesity and HCM remains limited. This study seeks to address this gap by investigating whether bariatric surgery, employed as a strategy for significant and lasting weight loss, is associated with a decreased risk of cardiovascular events necessitating acute care utilization in patients with obesity and HCM.
Method
This study utilized population-based data from the Statewide Planning and Research Cooperative System (SPARCS) spanning 2004 to 2014 to assess the impact of bariatric surgery on the risk of cardiovascular-related acute care events in patients with obesity and hypertrophic cardiomyopathy (HCM). SPARCS, a comprehensive all-payer reporting system, provided detailed patient-level information on demographics, diagnoses, treatments, and services in New York State.
The study focused on adult patients (aged ≥18 years) with both obesity and HCM, distinguishing between those who underwent bariatric surgery (bariatric surgery group) and those who underwent non-bariatric elective intra-abdominal surgery (control group). The control group was chosen to parallel post-surgical changes without weight intervention.
Identification of patients with obesity and HCM relied on diagnostic codes for HCM and obesity encounters during 2004 to 2014. Specific diagnostic codes (ICD-9-CM and ICD-10-CM) were employed to define HCM and its obstructive subtype. Obesity was defined using corresponding diagnostic codes.
The bariatric surgery group included patients with obesity and HCM who underwent bariatric surgery between January 1, 2004, and December 31, 2014. Bariatric surgery types were categorized using ICD-9 and ICD-10 codes, encompassing gastric bypass, gastric sleeve, and other procedures.
The control group comprised patients with obesity and HCM who underwent non-bariatric elective intra-abdominal surgery during the same period. Exclusions encompassed patients with multiple elective surgeries and those with diagnostic codes for gastrointestinal cancer.
Data analysis involved patient demographics, payment sources, diagnosis and procedure codes, and Elixhauser co-morbidity measures. The primary outcome assessed was cardiovascular-related acute care utilization, defined as emergency department visits or unplanned hospitalizations with a primary diagnosis of cardiovascular disease, identified through Clinical Classifications Software codes 96–121.
This study received approval from the Institutional Review Board of Columbia University Irving Medical Center. The follow-up period commenced on the surgery date for both groups.
Statistical Analysis
To compare baseline characteristics between patients undergoing bariatric surgery and those in the control group, statistical tests such as Student’s t-test or the χ2 test were employed as appropriate. The number of patients and the risk of the primary outcome event were then calculated for 1–6 months and 7–12 months post-surgery. Logistic regression models with generalized estimating equations were utilized to compare the risk of cardiovascular-related acute care utilization during these periods between the two groups. Multivariable models were applied to adjust for various factors, including age, sex, race/ethnicity, source of payment, hospital site, the number of prior emergency department visits or hospitalizations for cardiovascular disease within 2 years before surgery, and Elixhauser co-morbidity measures.
Furthermore, a propensity score (PS)-matched analysis was conducted to control for confounding by indication. PS-matching, based on a logistic regression model considering covariates such as age, sex, race/ethnicity, source of payment, prior ED visits or hospitalizations for cardiovascular disease, and Elixhauser co-morbidity measures, was performed at a 2:1 ratio without replacement and using callipers of width Z=0.1.
An inverse probability of treatment weighting (IPTW) analysis was also implemented. Similar to the PS-matched analysis, IPTW was computed using a logistic regression model with the same parameters. Stabilized weights, based on the inverse of the PS, were applied to generate a weighted cohort ensuring covariate distributions independent of treatment assignment.
Odds ratios (OR) of cardiovascular-related acute care utilization were estimated in univariable, multivariable, PS-matched, and IPTW models, with the control group as the reference. All statistical analyses were conducted at a 2-sided significance level of 0.05, and confidence intervals (CIs) were reported as two-sided values with a confidence level of 95%. The software used for these analyses was STATA 14.1 (StataCorp; College Station, TX).
Results
The study involved 207 adults with both obesity and hypertrophic cardiomyopathy (HCM), comprising 147 patients who underwent bariatric surgery (18 with gastric bypass, 72 with gastric sleeve, and 57 with other bariatric surgery) and 60 patients in the control group. Baseline characteristics indicated that patients in the bariatric surgery group were significantly older (P=0.01) and had a higher prevalence of females (P=0.02). Among these individuals, 100 had obstructive HCM, and 107 had non-obstructive HCM. No immediate deaths occurred following either bariatric or non-bariatric elective intra-abdominal surgery. At the 1-year follow-up, mortality rates were 10% in the bariatric surgery group and 9.5% in the control group (P>0.99).
Analyzing cardiovascular-related acute care use, the univariable analysis revealed no significant change in risk during the 1–6 months post-surgery period (OR 1.11; 95% CI 0.49–2.66; P=0.81). However, in the 7–12 months post-surgery period, the bariatric surgery group exhibited a significantly lower risk of acute cardiovascular events (OR 0.41; 95% CI 0.18–0.94; P=0.03) compared to the control group. Subgroup analyses based on HCM type (obstructive vs. non-obstructive) and bariatric surgery type (gastric bypass, gastric sleeve, or other) did not show significant differences in risk.
Multivariable analysis adjusting for potential confounders corroborated the univariable findings, revealing no significant differences in cardiovascular-related acute care use risk during the initial 6 months post-surgery. However, during the subsequent 7–12 months, patients who underwent bariatric surgery had a significantly lower risk (adjusted OR 0.23; 95% CI 0.068–0.71; P=0.01) compared with the control group.
In the propensity score (PS)-matched cohort, baseline characteristics were balanced, and consistent with previous analyses, patients undergoing bariatric surgery exhibited a significantly lower risk of cardiovascular-related acute care use during the 7–12 months post-surgery period (OR 0.26; 95% CI 0.083–0.73; P=0.01). No significant difference was observed during the initial 1–6 months post-surgery. The inverse probability of treatment weighting (IPTW) analysis replicated these findings, indicating a significantly lower risk of cardiovascular-related acute care use during the 7–12 months post-surgery period in patients who underwent bariatric surgery (OR 0.33; 95% CI 0.16–0.71; P=0.004).
Conclusion
In this population-based study encompassing 207 adults with obesity and hypertrophic cardiomyopathy (HCM), individuals who underwent bariatric surgery demonstrated a significantly lower risk of cardiovascular-related acute care use during the 7–12 months following surgery compared to the control group. This difference in risk reduction persisted across both univariable and multivariable models and remained consistent in analyses utilizing propensity score (PS)-matching and inverse probability of treatment weighting (IPTW) techniques. This study contributes novel findings by revealing the efficacy of bariatric surgery in reducing cardiovascular-related acute care events in patients concurrently experiencing obesity and HCM.
The effectiveness of bariatric surgery in achieving substantial weight loss is well-established, primarily studied in non-HCM populations. Previous research has highlighted significant improvements in cardiovascular disease (CVD) risk factors, such as a 77% resolution in diabetes mellitus and a 62% resolution in hypertension. These positive modifications in CVD risk factors have translated into a reduction in acute cardiovascular events, as demonstrated in large prospective cohort studies. In the present study, bariatric surgery showed a reduction in cardiovascular-related acute care utilization among patients with obesity and HCM, aligning with prior studies in non-HCM populations.
Recent years have witnessed an increased interest in understanding the clinical significance of obesity-associated acute cardiovascular events in HCM. Patients with HCM, particularly those with obesity, are prone to experiencing acute cardiovascular events. Despite the acknowledged importance, no prior studies have explored the impact of bariatric surgery, the most effective weight reduction method, on cardiovascular events in HCM patients. This study fills this gap by providing evidence that bariatric surgery does not elevate the risk of immediate postoperative cardiovascular events and exerts favorable effects in preventing cardiovascular-related acute care use in the longer term in individuals with HCM.
Cardiovascular-related acute care use, encompassing both emergency department visits and unplanned hospitalizations for cardiovascular disease (CVD), serves as a well-established outcome measure. This composite outcome is vital, reflecting clinically significant events associated with worsened quality of life and prognosis. By considering both ED visits and unplanned hospitalizations, the study provides valuable insights from a socioeconomic perspective, contributing information pertinent to patients and their families.
While HCM poses risks of sudden cardiac death, heart failure-related mortality, and stroke-related mortality, the study observed a 10% mortality rate within 1 year after surgery, which is relatively higher than reported rates. This emphasizes the need for further exploration and understanding of mortality patterns in this patient population undergoing bariatric surgery.
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